Combining root laws

๐Ÿ†Practice rules of roots combined

Combining root laws

What is a root?

A root is the inverse operation of exponentiation, denoted by the symbol โˆšโˆš, and it is equivalent to the power of 0.50.5.
If a small number appears on the left side, it indicates the order of the root.

Things to know about roots:

Square root of a product

(aโ‹…b)=aโ‹…b\sqrt{(a\cdot b)}=\sqrt{a}\cdot\sqrt{b}

Square root of a quotient

ab=ab\sqrt{\frac{a}{b}}=\frac{\sqrt{a}}{\sqrt{b}}

Square root of a square root

amn=anโ‹…m\sqrt[n]{\sqrt[m]{a}}=\sqrt[n\cdot m]{a}

Practice

The following exercise combines all the rules of roots,
can you solve it?

4โ‹…16+643โ‹…27+10โˆ’1+3=\sqrt{4\cdot16}+\sqrt{\frac{64}{3\cdot27}}+\sqrt{10-1}+3=

Solution:
Roots come before the order of operations, so we will first deal with the first root:
4โ‹…16=4โ‹…16\sqrt{4\cdot16}=\sqrt4\cdot\sqrt{16}
We could do this using the root formula of a product.
Let's move on to the second root:
643โ‹…27=6481=6481\sqrt{\frac{64}{3\cdot27}}=\sqrt{\frac{64}{81}}=\frac{\sqrt{64}}{\sqrt{81}}
Note โ€“ in this root, there was an exercise in the denominator, we first solved it and then continued to simplify the root using the root formula of a quotient.
Let's move on to the third root:
10โˆ’1=9\sqrt{10-1}=\sqrt9
Here we simply solved the exercise inside the root without using a formula.
Now let's rewrite the exercise slowly and carefully without getting confused:
4โ‹…16+6481โ‹…9+3=\sqrt4\cdot\sqrt{16}+\frac{\sqrt{64}}{\sqrt{81}}\cdot\sqrt9+3=
There are still roots in the exercise, so we will need to get rid of them:
2โ‹…4+89โ‹…3+3=2\cdot4+\frac{8}{9}\cdot3+3=
Now that there are no more roots, we can solve according to the order of operations:
8+223+3=13238+2\frac{2}{3}+3=13\dfrac{2}{3}

Start practice

Test yourself on rules of roots combined!

einstein

Choose the largest value

Practice more now

Combining root laws

It is also important to remember something fundamental, the important rules and the laws of roots.

What is a root?

A root is the inverse operation of exponentiation,
it is denoted by the symbol โˆšโˆš and is equivalent to the power of 0.50.5.
If a small number appears on the left side, it indicates the order of the root.

Join Over 30,000 Students Excelling in Math!
Endless Practice, Expert Guidance - Elevate Your Math Skills Today
Test your knowledge

What do you need to know about a root?

  1. The result of the root will always be positive! A negative result will never be obtained. We can get a result of 0.
  2. A root is essentially a power of one-half. We can say that: a=a12\sqrt a=a^{ 1 \over 2}
  3. Root comes before the four arithmetic operations. First, perform the root and only then arrange the arithmetic operations.

Laws of roots

Square root of a product

When the root appears over the entire product, we can break down each factor and apply the root while leaving the multiplication sign between the factors.
We will formulate it as a formula:
(aโ‹…b)=aโ‹…b\sqrt{(a\cdot b)}=\sqrt{a}\cdot\sqrt{b}

Square root of a quotient

When the root appears on the entire quotient (on the entire fraction), we can break down each factor and apply the root to it while leaving the division sign (the fraction line) between the factors.
We can formulate it as a formula:
ab=ab\sqrt{\frac{a}{b}}=\frac{\sqrt{a}}{\sqrt{b}}

Square root of a square root

The root on an additional root, we multiply the order of the first root by the order of the second root, and the order we obtained is applied as a root to our number. (Similar to the rule of power on power)
We will formulate this as a rule:
amn=anโ‹…m\sqrt[n]{\sqrt[m]{a}}=\sqrt[n\cdot m]{a}

Do you know what the answer is?

Practice

And now we will practice exercises that combine the laws of exponents:
9โ‹…16+2536โ‹…6โˆ’2=\sqrt{9\cdot16}+\sqrt{\frac{25}{36}}\cdot\sqrt{6-2}=

Solution:
According to what we learned, we must first handle the roots according to the order of operations, so we will start from the beginning of the exercise to handle each root.
Let's start with the root 9โ‹…16\sqrt{9\cdot16}
The root here is a root of a product, and according to the formula for a root with a product, we can separate the two numbers to solve more easily
(aโ‹…b)=aโ‹…b\sqrt{(a\cdot b)}=\sqrt{a}\cdot\sqrt{b}
In our exercise, this means
9โ‹…16=9โ‹…16\sqrt{9\cdot16}=\sqrt{9}\cdot\sqrt{16}
We will rewrite the exercise and continue
9โ‹…16+2536โ‹…6โˆ’2=\sqrt{9}\cdot\sqrt{16}+\sqrt{\frac{25}{36}}\cdot\sqrt{6-2}=
Great! Now let's move on to the second root that needs handling
2536\sqrt{\frac{25}{36}}
The root here is a root of a quotient, and according to the formula, we can separate the numerator and the denominator to make it easier to solve.
The formula is:
ab=ab\sqrt{\frac{a}{b}}=\frac{\sqrt{a}}{\sqrt{b}}

And in our exercise:
2536=2536\sqrt{\frac{25}{36}}=\frac{\sqrt{25}}{\sqrt{36}}
We will rewrite the exercise and continue:
9โ‹…16+2536โ‹…6โˆ’2=\sqrt{9}\cdot\sqrt{16}+\frac{\sqrt{25}}{\sqrt{36}}\cdot\sqrt{6-2}=
Now let's move to the root
6โˆ’2\sqrt{6-2}
Here, no formula is needed, and we can simply solve what is inside the root to get:
6โˆ’2=4\sqrt{6-2}=\sqrt4
Now we will rewrite the exercise:
9โ‹…16+2536โ‹…4=\sqrt{9}\cdot\sqrt{16}+\frac{\sqrt{25}}{\sqrt{36}}\cdot\sqrt{4}=
Note, according to what we learned, the root comes before arithmetic operations, so we will first solve the simple roots we created for ourselves:
9=3\sqrt9=3
16=4\sqrt{16}=4

2536=56\frac{\sqrt{25}}{\sqrt{36}}=\frac{5}{6}
4=2\sqrt4=2
Now let's rewrite the exercise after we have eliminated and solved all the roots:
3โ‹…4+56โ‹…2=3\cdot4+\frac{5}{6}\cdot2=
We will continue to solve according to the order of operations.
Multiplication comes before addition, therefore:
12+106=1346=132312+\frac{10}{6}=13\frac{4}{6}=13\frac{2}{3}

Check your understanding

Examples with solutions for Rules of Roots Combined

Exercise #1

Choose the largest value

Video Solution

Step-by-Step Solution

Let's begin by calculating the numerical value of each of the roots in the given options:

25=516=49=3 \sqrt{25}=5\\ \sqrt{16}=4\\ \sqrt{9}=3\\ We can determine that:

5>4>3>1 Therefore, the correct answer is option A

Answer

25 \sqrt{25}

Exercise #2

Solve the following exercise:

30โ‹…1= \sqrt{30}\cdot\sqrt{1}=

Video Solution

Step-by-Step Solution

Let's start with a reminder of the definition of a root as a power:

an=a1n \sqrt[n]{a}=a^{\frac{1}{n}}

We will then use the fact that raising the number 1 to any power always yields the result 1, particularly raising it to the power of half of the square root (which we obtain by using the definition of a root as a power mentioned earlier).

In other words:

30โ‹…1=โ†“30โ‹…12=30โ‹…112=30โ‹…1=30 \sqrt{30}\cdot\sqrt{1}= \\ \downarrow\\ \sqrt{30}\cdot\sqrt[2]{1}=\\ \sqrt{30}\cdot 1^{\frac{1}{2}}=\\ \sqrt{30} \cdot1=\\ \boxed{\sqrt{30}}

Therefore, the correct answer is answer C.

Answer

30 \sqrt{30}

Exercise #3

Solve the following exercise:

1โ‹…2= \sqrt{1}\cdot\sqrt{2}=

Video Solution

Step-by-Step Solution

Let's start by recalling how to define a square root as a power:

an=a1n \sqrt[n]{a}=a^{\frac{1}{n}}

Next, we remember that raising 1 to any power always gives us 1, even the half power we got from converting the square root.

In other words:

1โ‹…2=โ†“12โ‹…2=112โ‹…2=1โ‹…2=2 \sqrt{1} \cdot \sqrt{2}= \\ \downarrow\\ \sqrt[2]{1}\cdot \sqrt{2}=\\ 1^{\frac{1}{2}} \cdot\sqrt{2} =\\ 1\cdot\sqrt{2}=\\ \boxed{\sqrt{2}} Therefore, the correct answer is answer a.

Answer

2 \sqrt{2}

Exercise #4

Solve the following exercise:

16โ‹…1= \sqrt{16}\cdot\sqrt{1}=

Video Solution

Step-by-Step Solution

Let's start by recalling how to define a root as a power:

an=a1n \sqrt[n]{a}=a^{\frac{1}{n}}

Next, we will remember that raising 1 to any power will always yield the result 1, even the half power of the square root.

In other words:

16โ‹…1=โ†“16โ‹…12=16โ‹…112=16โ‹…1=16=4 \sqrt{16}\cdot\sqrt{1}= \\ \downarrow\\ \sqrt{16}\cdot\sqrt[2]{1}=\\ \sqrt{16}\cdot 1^{\frac{1}{2}}=\\ \sqrt{16} \cdot1=\\ \sqrt{16} =\\ \boxed{4} Therefore, the correct answer is answer D.

Answer

4 4

Exercise #5

Solve the following exercise:

1โ‹…25= \sqrt{1}\cdot\sqrt{25}=

Video Solution

Step-by-Step Solution

To solve the expression 1โ‹…25 \sqrt{1} \cdot \sqrt{25} , we will use the Product Property of Square Roots.

According to the property, we have:

1โ‹…25=1โ‹…25\sqrt{1} \cdot \sqrt{25} = \sqrt{1 \cdot 25}

First, calculate the product inside the square root:

1โ‹…25=251 \cdot 25 = 25

Now the expression simplifies to:

25\sqrt{25}

Finding the square root of 25 gives us:

55

Thus, the value of 1โ‹…25 \sqrt{1} \cdot \sqrt{25} is 5\boxed{5}.

After comparing this solution with the provided choices, we see that the correct answer is choice 3.

Answer

5 5

Start practice